Note: Descriptions are shown in the official language in which they were submitted.
Pressure wave generator
Field of the invention
The invention relates to a pressure wave generator (DWG) and a
system for generating a pressure wave, as well as a method for generating a
pressure
wave and a use of the DWG, system or method.
Background
DWGs can be used to clean a dirty tank, pipe or steam boiler, e.g. in
a power plant. Such a DWG is described, for example, in WO 2021/078754 Al.
Compressed air is forced into a pressure chamber, e.g. at 100 bar. When the
air sud-
denly flows out of the pressure chamber, a very fast air flow is generated,
which cre-
ates a strong pressure wave with high total pressure in the vicinity of the
DWG. When
this pressure wave hits the contaminated surfaces of the tank, pipe or steam
boiler, it
exerts a strong force on the existing contaminants, e.g. deposits and caking,
and blasts
them away.
Known DWGs have various disadvantages: On the one hand, they
have a large form factor due to the volumes of compressed air required and a
high
weight, particularly in the range of several hundred kilograms. As a result,
such
DWGs can hardly be used for mobile applications and in particular cannot be
maneu-
vered by hand, and they cannot be brought into the room that is to be cleaned.
On the
other hand, some of the potential energy stored with the compressed air in the
DWG
is dissipated either inside the DWG, e.g. by impacts on the walls of the
pressure
chamber, or outside due to the undirected propagation of the pressure wave,
e.g. in di-
rections in which there is no contamination.
Disclosure of the invention
There is therefore a need for an improved pressure wave generator
(DWG). One possible object of the invention is to provide a DWG that can be
maneu-
vered by hand and, in particular, can also be used in places that are
difficult to access.
Another possible object of the invention is to provide a DWG with an increased
cleaning effect. Furthermore, an object of the invention can be seen in
providing a
correspondingly improved method for generating a pressure wave.
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Pressure wave generator
One or more of the above problems are solved by the DWG accord-
ing to the invention, which is designed to generate a pressure wave in the
environ-
ment of the DWG and, in particular, to cause a cleaning effect via the
pressure wave,
e.g. on a contaminated container, a contaminated pipe or a steam boiler. Such
a DWG
comprises
- a pressure chamber which can be filled with a working medium, in
particular compressed air, via a pressure chamber inlet, with at least two
pressure out-
lets located opposite each other;
- an actuator chamber which can be filled with an actuator medium,
in particular compressed air, via an actuator chamber inlet,
- at least two actuator outlets opposite each other, which are con-
nected to the pressure chamber by a passage;
- a closure element in the pressure chamber which, in a closed posi-
tion, closes the pressure chamber with respect to the pressure outlets and, in
an open
position, allows the working medium to flow out through the pressure outlets:
The
closure element in the pressure chamber is arranged at least partially between
the pas-
sage and the pressure outlets. Advantageously, the closure element can be
moved
from the closed position to the open position by sliding it in an axial
direction. The
pressure outlets are advantageously arranged essentially radially outwards. In
this
context, "radial" is to be understood as any direction that is orthogonal to
"axial". "Es-
sentially radial" shall in particular include deviations of up to 450, in
particular up to
30 , from the radial direction;
- an actuator element in the actuator chamber which, in a closed po-
sition, closes the pressure chamber with respect to the actuator outlets and,
in an open
position, allows the working medium to flow out, in particular from the
pressure
chamber through the passage and the actuator outlets: The actuator element is
ar-
ranged in the actuator chamber between the actuator chamber inlet and the
passage.
Advantageously, the actuator chamber inlet is sealed against the passage by
the actua-
tor element, which in particular has no passage opening. Advantageously, the
actuator
element can also be moved from the closed position to the open position by
sliding it
in the axial direction. The actuator outlets are advantageously arranged
essentially ra-
dially outwards.
In operation with the working medium, the closure element can be
moved from the closed position to the open position by moving the actuator
element
from the closed position to the open position. This can be achieved in
particular by a
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"pneumatic actuator" comprising the actuator element and, advantageously, a
second
actuator element, as shown below.
Pressure chamber and actuator chamber
In an embodiment, the pressure chamber is essentially cylindrical
and the closure element comprises a hollow cylinder that is open on one end
face. An
opposite end face of the hollow cylinder is essentially closed. However, the
opposite
end face can have a passage opening, in particular centrally arranged, through
which
an interior of the hollow cylinder can be filled with the working medium. In
this case,
an outer surface of the closure element must lie tightly and in particular gas-
tightly
against an inner surface of the pressure chamber. In particular, a seal is
fitted between
the outer surface of the closure element and the inner surface of the pressure
chamber.
Advantageously, the closed end face of the closure element has an
inner surface facing the interior that is, in particular, at least 5% smaller
than an oppo-
site outer surface. This has the effect that the closure element also remains
in the
closed position when the pressure chamber is closed, in particular when the
actuator
element is in the closed position. According to the general formula F = p=A,
the dif-
ference in the area A between the outer surface and the inner surface of the
closure el-
ement results in an effective force F on the closure element in the direction
of the
closed position, as the pressure p is the same on both sides in the stationary
state.
If the passage is opened, in particular by moving the actuator ele-
ment to the open position, working medium flows out through the passage and
the ac-
tuator outlets. This causes the pressure on the outer surface of the closure
element to
drop rapidly. On the inner surface of the closure element, on the other hand,
the pres-
sure is reduced only slowly, namely as long as the closure element is in the
closed po-
sition, only via the passage opening. As a result, an effective force acts on
the closure
element in the direction of the open position and the closure element is moved
into
the open position, whereby the pressure outlets of the pressure chamber are
opened
and the working medium, in particular from the interior of the closure
element, es-
capes quickly. By "quickly" it is understood in particular that a half-value
time of the
pressure of the working medium in the pressure chamber after moving the
actuator el-
ement into the open position is at most 10 ms, in particular at most 6 ms.
In general, the DWG generates a pressure wave both at the pressure
outlets and at the actuator outlets. The arrangement described therefore
effectively
uses the entire volume, in particular both the partial volume on the outer
surface of
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the closure element and the partial volume on the inner surface of the closure
ele-
ment, of the pressurized working medium in the pressure chamber to generate
pres-
sure waves with a cleaning effect. This achieves an increased cleaning effect.
In one embodiment, the pressure chamber is between 1.2 and 2
times, in particular between 1.4 and 1.7 times, as large as the interior of
the closure
element. This makes it easy to move the closure element between the closed and
open
positions. In particular, the interior of the closure element can have a
volume of 1 to 2
liters and the pressure chamber a volume of one and a half to 3 liters.
Furthermore,
the closure element can have an outer diameter of 100 to 150 mm.
The passage opening in the closure element advantageously has a
diameter of between 1 and 10 mm, in particular between 3 and 5 mm. Such a
dimen-
sioning enables easy movement of the closure element between the closed and
open
position and at the same time rapid filling of the pressure chamber with
working me-
dium, e.g. within a maximum of 5 s, in particular a maximum of 3 s.
In an embodiment, the pressure chamber can be filled with the
working medium, in particular air, at a pressure of at least 100 bar, in
particular at
least 200 bar. In addition, the actuator chamber can advantageously be filled
with the
actuator medium, which is advantageously the same as the working medium, at a
pressure of at least 10 bar. With such a dimensioning, the pressure chamber
can, for
example, be filled with a volume of air that has a volume of at least 150
liters, in par-
ticular at least 300 liters, at 1 bar. In particular, a speed of at least 15
m/s, especially
at least 30 m/s, can be achieved when moving the closure element from the
closed to
the open position. This generates a sufficiently strong pressure wave so that
even per-
sistent dirt, e.g. caked-on soot or corrosion products such as lust, can be
removed.
In addition, the actuator element, which closes the passage from the
pressure chamber in its closed position, must be dimensioned depending on the
pres-
sure of the working medium and the pressure of the actuator medium so that it
re-
mains in the closed position when the pressure chamber and actuator chamber
are
full. The actuator element should only be moved to the open position when the
pres-
sure of the actuator medium is reduced. This is achieved by one end face of
the actua-
tor element, which is directed towards the passage, being smaller than an
opposite
end face, which is directed towards the actuator chamber inlet. The required
ratio of
the end faces can be calculated - depending on the pressures of the actuator
medium
and the working medium - using the general formula F = p.A.
Pressure outlets and actuator outlets
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The fact that the at least two pressure outlets are arranged opposite
each other, in other words symmetrically, in particular axially symmetrically
on the
DWG, has the effect that at least the radial components of the recoil forces
on the
DWG caused by the outflowing working medium cancel each other out. The same ap-
plies to the at least two actuator outlets, which are also located opposite
each other on
the DWG. In this way, the DWG can be operated hand-held. The DWG can therefore
be designed as a mobile device that can be held manually, e.g. in a dirty
boiler. With-
out a special arrangement of the outlets, the recoil forces of the outflowing
working
medium would make the DWG too large and mobile handling impossible.
In an embodiment, the total opening area of the pressure outlets is at
least as large, in particular at least 20 % larger, than the open end face of
the hollow
cylinder. This enables a rapid outflow of the working medium from the pressure
chamber as soon as the closure element is in the open position, and thus a
high out-
flow velocity and a strong pressure wave. Advantageously, the outflow velocity
at a
narrowest point, e.g. in the pressure outlets, is approximately Mach 1, so
that the
strongest possible pressure wave is achieved. In addition, the described
dimensioning
of the pressure outlets prevents the working medium from exerting excessive
forces
on components of the DWG, in particular adjacent to the pressure outlets,
during out-
flow, which could lead to damage to the DWG, at least in the long term.
In an embodiment, the at least two pressure outlets on at least two
sides of the pressure wave generator each comprise at least three outlet
openings. The
outlet openings can be designed with an essentially square cross-section. Such
a de-
sign of the pressure outlets results in a strong pressure wave which is
directed in an
angular range of, for example, 90 degrees and thus achieves a good cleaning
effect in
this angular range.
The actuator outlets may also comprise one or more outlet open-
ings, e.g. in the form of elongated outlet slots or, in particular, with a
square cross-
section. Here too, the shape of the outlets can be used to influence the
strength and di-
rectional characteristic of the pressure wave generated.
Furthermore, it is advantageous that the at least two actuator outlets
are essentially oriented in the same way as the at least two pressure outlets,
in particu-
lar with a deviation of no more than 30 degrees.
In particular, the actuator outlets can be arranged at essentially the same
angular posi-
tion on the DWG as the pressure outlets. Such an arrangement has the effect
that the
pressure waves generated at the actuator outlets and at the pressure outlets
are di-
rected into the same angular range and reinforce each other in their cleaning
effect.
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In an embodiment, a total opening area of the actuator outlets or of
the passage to the actuator outlets is smaller than the total opening area of
the pres-
sure outlets. In particular, the total opening area of the actuator outlets or
the passage
can be less than half as large as the total opening area of the pressure
outlets. This has
the advantage that the pressure of the working medium reduces more slowly via
the
actuator outlets than via the pressure outlets when the closure element is
moved into
the open position, so that the working medium remaining in the pressure
chamber on
the outside of the closure element acts as a gas spring and dampens the
movement of
the closure element. This in turn avoids a strong impact of the closure
element on the
inside of the pressure chamber and thus improves both the manageability and
the ser-
vice life of the DWG.
Second actuator chamber
In an advantageous embodiment, the DWG additionally comprises
- a second actuator chamber, which can be filled with the actuator
medium via a second actuator chamber inlet, with at least two second actuator
outlets
located opposite one another: The second actuator chamber and the actuator
chamber
are connected by a second passage. This second passage corresponds
advantageously
to the actuator chamber inlet;
- a second actuator element in the second actuator chamber which,
in a closed position, closes the actuator chamber and the second actuator
chamber
with respect to the second actuator outlets and, in an open position, allows
the actua-
tor medium to flow out through the second passage and the second actuator
outlets:
The second actuator element is arranged in the second actuator chamber between
the
second actuator chamber inlet and the second passage.
For a simple and compact design, the actuator chamber can be filled
with the actuator medium via the second actuator chamber and the second
actuator
chamber inlet.
Advantageously, the second actuator chamber and the second actua-
tor element are cylindrical. The cylindrical shape generally has the advantage
that the
pressure forces are distributed without acting excessively on individual
components
or wall parts, and that at the same time the (second) actuator element in the
(second)
actuator chamber or the closure element in the pressure chamber can be
displaced in
the manner of a piston.
Furthermore, the second actuator element can have a passage open-
ing, in particular a central one. The actuator chamber can also be filled with
actuator
CA 03241007 2024-6- 13
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medium from the second actuator chamber inlet via this passage opening.
Advanta-
geously, the second actuator element - similar in principle to the closure
element - is
shaped such that an end face aligned with the actuator chamber is smaller, in
particu-
lar at least 5 % smaller, than an end face aligned with the second actuator
chamber in-
let. This in turn has the effect, as described above in connection with the
closing ele-
ment, that the second actuator element remains in the closed position when the
actua-
tor chamber and the second actuator chamber are filled and, thus, closes the
second
actuator outlets. As a result, the actuator element and the closure element
also remain
in the closed position and the pressure chamber can be filled with working
medium.
In an advantageous embodiment, the DWG further comprises a con-
trollable drain valve, in particular for the second actuator chamber inlet,
for triggering
the draining of actuator medium from the actuator chamber. Advantageously, the
drain valve comprises a solenoid valve. By opening the drain valve, the above-
men-
tioned "pneumatic actuator" is actuated as follows: The pressure in the second
actua-
tor chamber decreases as actuator medium flows out through the drain valve. As
a re-
sult, an effective force acts on the second actuator element in the direction
of the open
position and moves it into the open position so that the second actuator
outlets are re-
leased. The actuator medium now also flows out of the actuator chamber
quickly, in
particular via the second actuator outlets. As a result, the pressurized
working me-
dium exerts an effective force on the actuator element in the direction of the
open po-
sition. The actuator element is moved into the open position and releases the
actuator
outlets so that working medium flows out there, the closure element moves into
the
open position as described above and pressure waves are generated.
Further aspects of the DWG
It is unavoidable that the flow of the working medium when flow-
ing out of the pressure outlets also has an axial component of the flow
velocity in ad-
dition to the radial component, especially while the closing element is moving
into
the open position. As a result, the recoil force on the DWG also includes an
axial
component, which is not compensated for by the clever arrangement of the
pressure
outlets described above and causes an undesirable impact on the operator,
particularly
under manual operation.
To minimize this recoil, in an advantageous embodiment at least
one projection is provided on an outer side of the DWG adjacent to the at
least two
pressure outlets in the direction of the end face of the DWG. At the same
time, the
pressure outlets should also be arranged in a part of the pressure chamber
facing the
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end face of the DWG and, in particular, the closure element should be in a
position
close to the end face in its closed position, while it is in a position remote
from the
end face in the open position. Such an arrangement of the pressure outlets
leads to an
axial component of the flow velocity of the outflowing working medium in the
direc-
tion of the end face. The protrusions are advantageously arranged in such a
way that
they influence and, in particular, deflect the flow of the working medium
flowing out
through the pressure outlets. When the flow hits the projections, a force acts
on the
DWG which at least partially compensates for the axial component of the recoil
force,
in particular by at least 50 %. Suitable protrusions are, for example, ribs,
which pro-
trude at least 1 cm and advantageously run parallel to the end faces. In an
advanta-
geous embodiment, the at least one projection is designed as a ring running
around
adjacent to the at least two pressure outlets.
In this way, a DWG can be provided that can be held by hand dur-
ing operation, in other words it can be operated hand-held. Such manual
maneuvera-
bility facilitates, accelerates and improves the cleaning of dirty containers,
as the
DWG can be held at the points to be cleaned without great effort, e.g. by
repeated as-
sembly.
The weight of the DWG naturally also plays an important role here.
Advantageously, the DWG has a weight of no more than 12 kg, in particular no
more
than 7 kg. This can be achieved by making key components of the DWG, in
particular
the pressure chamber, the actuator chamber, the second actuator chamber, the
closure
element, the actuator element and/or the second actuator element, from
aluminum. A
low weight in turn improves handling.
System for generating a pressure wave
A further aspect of the invention relates to a system for generating a
pressure wave. The system comprises the DWG described above and a lance to the
distal end of which the DWG is attached. At the proximal end of the lance, the
system
can be held by a user and controlled from there. The lance comprises a first
supply
line for working medium and a second supply line for actuator medium. In
addition,
the lance advantageously comprises a control line for controlling the drain
valve, e.g.
an electrical line in the case of a solenoid valve.
Such a system makes it possible to clean dirty containers, in particu-
lar pipes or boilers, even in remote locations without the user having to
enter the con-
tainer themselves. For this purpose, the lance may be at least 3 m long, in
particular at
least 5 m long. In particular, such a system makes it possible to clean
contaminated
CA 03241007 2024-6- 13
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containers during operation, e.g. in the case of a power plant or generator,
without
shutting it down.
For the latter application in particular, the DWG or system must be
designed to withstand temperatures of several hundred degrees Celsius, in
particular
at least 900 degrees Celsius. The following embodiment is advantageous for
this pur-
pose: The lance comprises a multi-chambered hollow profile. An outer chamber
of
the hollow profile is designed to supply cooling water and/or cooling air for
the DWG
to the distal end of the lance. At the distal end, the lance can in particular
have outlet
openings that are arranged in such a way that the cooling water trickles or
flows over
the DWG during operation and cools it. Furthermore, the first and second
supply lines
and, in particular, the control line run in an inner chamber of the hollow
profile. In
this way, the supply lines and the control line are also protected from the
high temper-
atures during operation, which enables cleaning at high temperatures,
especially when
the power plant is in operation.
In a further embodiment, the system comprises a camera that is at-
tached to the pressure wave generator, in particular to the end face of the
pressure
wave generator, and is set up to inspect an area surrounding the pressure wave
gener-
ator. An infrared camera (IR camera) has proven to be particularly suitable
for in-
specting contaminated areas. The camera can speed up and/or improve the
cleaning of
soiled containers, as soiled areas can be better recognized and the DWG can be
better
aligned to these areas.
Advantageously, the system also comprises at least one storage bottle to which
the
first and second supply lines are connected. The at least one storage bottle
can, for ex-
ample, contain a total volume of 200 to 300 liters of the working or actuator
medium.
In practice, the at least one storage bottle can be filled with working or
actuator me-
dium using a compressor up to a pressure of over 300 bar, e.g. 330 bar. A
compressor
with a capacity of at least 500 to 800 liters/min at 330 bar has proven to be
particu-
larly practical for this purpose.
Method for generating a pressure wave
A further aspect of the invention relates to a method for generating
a pressure wave, in particular for cleaning contaminated containers. In
particular, the
method is carried out using the DWG described above and comprises the
following
steps:
(a) Filling the actuator chamber with a gaseous actuator medium at
a pressure above 10 bar, in particular below 50 bar;
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(b) Filling the pressure chamber with a gaseous working medium at
a pressure of over 100 bar, in particular over 200 bar;
(c) Moving the actuator element from the closed position to the
open position, thereby moving the closure element from the closed position to
the
open position and thereby releasing the pressurized working medium from the
pres-
sure chamber through the pressure outlets and the actuator outlets: As
explained
above, the rapid release due to the high pressure of the working medium in the
pres-
sure chamber creates a pressure wave at the pressure outlets and the actuator
outlets,
which has a good cleaning effect.
For a good cleaning effect, it is advantageous that the pressurized
working medium is released from the pressure chamber in step (c) with a half-
value
time of less than 10 ms, in particular less than 6 ms. Such half-value times
can be
achieved with a DWG with the dimensions described above.
In an embodiment, the working medium and in particular the actua-
tor medium is air. In particular, the pressure chamber can be filled with a
volume of
air that has a volume of at least 150 liters, in particular at least 300
liters, at 1 bar.
Furthermore, in an embodiment with a second actuator chamber, it
is advantageous that the actuator chamber is filled in step (a) via the second
actuator
chamber and the passage opening in the second actuator element. This avoids a
sepa-
rate inlet for the actuator chamber and enables a compact design. The pressure
cham-
ber, on the other hand, advantageously has its own pressure chamber inlet.
In addition, the movement of the actuator element in step (c) is ef-
fected in an embodiment by draining actuator medium from the actuator chamber
through the actuator chamber inlet and in particular by draining actuator
medium
from the second actuator chamber via the second actuator chamber inlet, in
particular
by opening the drain valve, see the above description of the "pneumatic
actuator".
In continuous operation when cleaning a contaminated container,
the DWG is usually not only actuated once, i.e. it does not only generate a
single
pressure wave, but "shoots" at regular intervals. Advantageously, the method
there-
fore comprises repeating steps (a), (b) and (c) with a pressure wave interval
of at most
s, in particular at most 5 s. Theoretically, therefore, at least 6, in
particular at least
12, "shots", i.e. pressure waves, are generated per minute. In particular, the
method
for cleaning the container additionally comprises moving the DWG to a next
location
to be cleaned, in particular by hand.
Use of the DWG
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11
The features of the DWG or the system for generating a pressure
wave described above are meant to be also disclosed in connection with said
method
and vice versa. Furthermore, the invention relates to a use of the DWG, the
system or
the method for cleaning a contaminated vessel, tube or steam boiler. Such
vessels,
pipes and steam boilers are typically part of a power plant, e.g. a coal-fired
power
plant, waste-fired power plant, biomass-fired power plant or gas turbine power
plant.
When used in a coal-fired power plant, the DWG will therefore pri-
marily clean the surfaces of the container from soiling caused by combustion
prod-
ucts, e.g. soot. As described, this can even be done while the power plant is
in opera-
tion, i.e. while hot flue gases are circulating in the container.
When used in a gas turbine combined cycle power plant, the DWG
will primarily remove rust from the finned tube surfaces of the downstream
steam
boiler. The rust is formed as a corrosion product during the further
utilization of the
residual heat contained in the flue gas.
If the environment of the DWG is rather cool, in particular below
100 degrees Celsius, e.g. with downstream boilers in a gas turbine power
plant, an ar-
rangement with a wire rope hoist is also conceivable instead of the system
with lance
described above. In this case, the DWG is attached to a rope hoist, which is
config-
ured such that the DWG can reach and clean the entire surface of a tube bundle
in the
tank. In particular, the position of the DWG may be automatically controlled
via the
rope hoist and a computer-implemented control system and adapted to the
respective
container.
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Brief description of the drawings
Further embodiments, advantages and applications of the invention
are apparent from the dependent claims and from the following description of
the fig-
ures. These show:
Figure 1 a schematic drawing of a pressure wave generator (DWG)
according to an embodiment of the invention;
Figures 2 and 3 schematic drawings of systems for generating a
pressure wave according to embodiments of the invention in use.
Ways to carry out the invention
The structure of a DWG is shown schematically in Fig. 1. A hous-
ing 16, which is advantageously made of aluminum for weight reasons, encloses
a
pressure chamber, which consists of the interior 12 and the gas spring chamber
11, an
actuator chamber 18 and a second actuator chamber 19.
In the pressure chamber 11, 12, which has a cylindrical shape, there
is a hollow cylinder 13, which acts as a closure element as described above.
The hol-
low cylinder 13 encloses the interior 12 and, in its closed position (as shown
in Fig.
1), closes pressure outlets 15 from the pressure chamber 11, 12 to the
surroundings of
the DWG. The hollow cylinder may have an outer diameter of approx. 0.1 m, for
ex-
ample. The volume of the inner chamber 12 can be e.g. approx. 1 liter, the
volume of
the gas spring chamber 11 e.g. approx. 0.6 liter. In order to prevent working
medium
from flowing out of the gas spring chamber 11 through the pressure outlets 15,
a seal
13a, e.g. an 0-ring with Teflon, is fitted between the hollow cylinder 13 and
the inner
wall of the housing 16.
For optimum sealing, the housing 16 can generally have a sealing
layer 14, in particular made of Teflon, on the end face of the DWG, against
which the
hollow cylinder 13 is pressed in the closed position. The pressure chamber can
be
filled with a pressurized working medium, e.g. air, via a valve-controlled
supply line
10. The pressure of the working medium in the pressure chamber may be over 200
bar in order to generate a powerful pressure wave with a good cleaning effect.
When
the pressure chamber is closed, this pressure acts both in the gas spring
chamber 11
and in the interior 12, as it is equalized via a passage opening 17 in the
hollow cylin-
der 13 and a state of equilibrium is established.
An actuator element 6 is located in the actuator chamber 18, which
also has a cylindrical shape. In its closed position (as shown in Fig. 1), the
actuator
CA 03241007 2024-6- 13
13
element 6 closes a passage 7 between the pressure chamber, in particular the
gas
spring chamber 11, and the actuator outlets 8. The actuator element 6 seals
against the
inner wall of the actuator chamber 18. For this purpose, a sealing ring 6a,
e.g. com-
prising Teflon, can be inserted into the inner wall of the actuator chamber,
for exam-
ple.
In the second actuator chamber 19, there is a second actuator ele-
ment 2, which (like the hollow cylinder 13) has a through-hole 5. In its
closed posi-
tion (as shown in Fig. 1), the second actuator element 2 closes a passage 3
between
actuator chamber 18 and second actuator outlets 4. The second actuator element
2 is
also sealed against the inner wall of the housing by means of a seal 2a, e.g.
an 0-ring
with Teflon.
The second actuator chamber 19 and the actuator chamber 18 are
filled with actuator medium, e.g. air, under pressure from a valve-controlled
supply
line 1 via the through-hole 5. A release valve 9, which is also fitted at the
inlet to the
second actuator chamber 19, is closed. The pressure in the actuator chamber 18
is typ-
ically significantly lower, in particular by approximately one order of
magnitude, than
the pressure in the pressure chamber. In particular, the actuator chamber 18
is filled
with air at a pressure of between 8 and 25 bar, e.g. approx. 20 bar.
The supply valves 1, 10 and the drain valve 9 are advantageously
solenoid valves that can be controlled via an electrical pulse. The control
system is
advantageously designed as a computer or hardware-implemented control system
so
that the valves open and close automatically during operation.
It is advantageous for the drain valve 9 to be located close to the
second actuator chamber 19 in order to enable the actuator medium to be
drained
quickly. In particular, the drain valve should be located no more than 1 m
away from
the second actuator chamber 19. For reasons of robustness and compact design,
it is
advisable for the drain valve 9 to be integrated in the housing 16. The supply
valves
1, 10, on the other hand, can be further away from the housing 16, e.g. at the
end of
the lance or more than 1 m or more than 3 m away from the housing 16. In
particular,
if the DWG is attached to a lance, as described above, the supply valves 1, 10
may be
located in a supply and control unit which e.g. also contains pressurized gas
cylinders
and is connected upstream of the lance. This has the advantage that the system
con-
sisting of lance and DWG, which is intended to be mobile, has a lower weight
and
can therefore be held by hand.
A "firing cycle", in which a pressure wave is generated during oper-
ation of the DWG, proceeds as follows:
CA 03241007 2024-6- 13
14
1. The supply valve 1 for the actuator medium is opened. The ac-
tuator pressure rises in front of the second actuator element 2 and presses it
into its
seat in the passage 3, closing the second actuator outlets 4. Valves 9 and 10
remain
closed during this phase.
2. The actuator medium now flows through the small through-
hole 5 to the actuator element 6 and presses it into the seat in passage 7,
i.e. in the
closed position, whereby the actuator outlets 8 are closed.
3. The power supply valve 10 is opened and the gas spring cham-
ber 11 and the interior 12 via the small passage opening 17 in the hollow
cylinder or
piston 13 are filled with working medium. The gas spring piston surface is
larger than
the piston inner surface, the gas spring force therefore presses the piston 13
towards
the end face into the soft seal 14, i.e. into the closed position, and thus
closes the ra-
dial pressure outlets 15. The DWG is now charged.
4. The supply valves 1 and 10 are closed.
5. The drain valve 9 is opened: The drive pressure behind the sec-
ond actuator element 2 drops and the actuator element is opened by the now
higher
pressure force on the passage side 7. The drive pressure of the actuator
element 6 es-
capes via the second actuator outlets 4 and the pressure of the working medium
in the
gas spring chamber 11 pushes the actuator element 6 open (open position) and
re-
leases the radial actuator openings 8.
6. The gas spring air escapes via the actuator openings 8 and re-
lieves the gas spring 11. The internal piston pressure in the interior 12 is
now greater
than the gas spring pressure in the gas spring chamber 11, and the piston 13
is moved
backwards, i.e. into the open position, by the differential force and opened
at high
speed. As a result, the working medium now escapes from the piston 13 radially
out-
wards via the pressure outlets 15.
When the working medium escapes rapidly from the gas spring
chamber 11 through the actuator outlets 8 and from the interior 12 through the
pres-
sure outlets 15, strong pressure waves are created in the surrounding gas. The
pres-
sure waves propagate in the environment and clean the surfaces from
contamination
when they hit them.
To ensure that the DWG can be operated hand-held, some precau-
tions must be taken as described above, as the recoil of the outflowing
working me-
dium would otherwise tear the DWG out of a user's hand. On the one hand, the
pres-
sure outlets 15 are arranged opposite each other on the housing 16; the same
applies
to the actuator outlets 8.
CA 03241007 2024-6- 13
15
On the other hand, it is advantageous that projections 20, e.g. in the
form of ribs or a circumferential ring, are attached to the outside of the
housing 16
next to the pressure outlets 15. Outflowing gas with an axial component of the
flow
hits the projections 20. As explained above, the axial recoil exerted by the
outflowing
working medium on the pressure chamber 11, 12 and the piston 13 and the
oppositely
directed impact of the working medium on the projections 20 at least partially
com-
pensate each other. This in turn enables easier handling of the DWG.
Fig. 2 shows a system consisting of DWG 24 and lance 25, on
which the DWG 24 is mounted, in use in a steam boiler. Tube bundles 23 with a
large
number of heat exchanger tubes are installed in the convective pass 21 of the
steam
boiler, covering the entire flow cross-section of the boiler. Hot flue gas 22
flows
through the tube bundles 23, known as "bundles" for short, past the heat
exchanger
tubes and transfers its heat to the tubes. As the flue gas 22 often carries
combustion
products with it, which settle or condense on the bundles 23, soiling occurs
there, e.g.
in the form of soot and caking. Between every two bundles 23 there is an
intermediate
space 27, called an alley, which is accessible via a boiler door 28. The side
length of
the, e.g. square, boiler cross-section is typically between 3 and 25 m.
A DWG 24 according to the invention can be used to remove this
contamination. For this purpose, the DWG 24 can be introduced into the alley
27
through the boiler door 28 with the aid of the lance 25. Advantageously, the
lance 25
is over 3 m long and up to 12 m long, for example, in order to be able to
clean larger
boilers with a side length of up to 25 m that are accessible from both sides.
In the al-
ley 27, the DWG 24 generates strong pressure waves 26, ideally directed at the
bun-
dles 23 and the soiling. The optimized manageability described above allows
the
lance 25 to be held by hand even in "shooting mode". Furthermore, in one
embodi-
ment of the system with water cooling in particular, it is not even necessary
to switch
off the hot gas flow 22. The steam boiler 21 and bundles 23 can therefore be
cleaned
during operation.
Fig. 3 shows an alternative installation of a DWG 32 in a vessel in
the form of a boiler 31, e.g. a downstream steam boiler in a gas-fired
combined cycle
power plant. The DWG 32 is suspended from ropes 35 in the boiler 31. At the
same
time, the supply lines for the working and actuator medium and the control
line may
also run along the ropes 35. The position of the DWG 32 can be controlled via
motor-
driven rollers 36, over which the ropes 35 run. The control of the position of
the
CA 03241007 2024-6- 13
16
DWG 32 and the "shots", i.e. the generation of the pressure waves 33, is
preferably
carried out automatically, e.g. via a computer-implemented control system 37.
Another advantageous feature is a camera 34, which is attached to
the DWG 32. This allows particularly dirty areas to be detected and the
cleaning suc-
cess to be estimated. It is also conceivable to control the position and the
"shots" of
the DWG 32 in real time via the computer-implemented control 37 depending on
the
images taken by the camera 34.
While preferred embodiments of the invention are described in the
present application, it should be noted that the invention is not limited
thereto and
may be practiced in other ways within the scope of the following claims.
CA 03241007 2024-6- 13
